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CVE-2026-44309

gitsign verify accepts signatures over go-git-normalized bytes, enabling trust confusion on malformed commits

5.3 MediumFix available

Gitsign is a keyless Sigstore to signing tool for Git commits with your a GitHub / OIDC identity. Prior to 0.16.0, gitsign verify and gitsign verify-tag re-encode commit/tag objects through go-git's EncodeWithoutSignature before checking the signature, instead of verifying against the raw git object bytes. For malformed objects with duplicate tree headers, git-core and go-git parse different trees: git-core uses the first, go-git uses the second. A signature crafted over the go-git-normalized form (second tree) passes gitsign verify while git-core resolves the commit to a completely different tree. This breaks the invariant that a verified signature, the commit semantics git-core presents to users, and the object hash logged in Rekor all refer to the same content. This vulnerability is fixed in 0.16.0.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
None
Integrity
High
Availability
None

Exploit likelihood

0.14%Up 0.1 points since May 16, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.3

gitsign verify accepts signatures over go-git-normalized bytes, enabling trust confusion on malformed commits

Gitsign is a keyless Sigstore to signing tool for Git commits with your a GitHub / OIDC identity. Prior to 0.16.0, gitsign verify and gitsign verify-tag re-encode commit/tag objects through go-git's EncodeWithoutSignature before checking the signature, instead of verifying against the raw git object bytes. For malformed objects with duplicate tree headers, git-core and go-git parse different trees: git-core uses the first, go-git uses the second. A signature crafted over the go-git-normalized form (second tree) passes gitsign verify while git-core resolves the commit to a completely different tree. This breaks the invariant that a verified signature, the commit semantics git-core presents to users, and the object hash logged in Rekor all refer to the same content. This vulnerability is fixed in 0.16.0.

Record
CVE-2026-44309
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
Weakness
CWE-347, CWE-295
Updated
2026-11-02
EUVDEUVD-2026-30563 5.3

Gitsign is a keyless Sigstore to signing tool for Git commits with your a GitHub / OIDC identity. Prior to 0.16.0, gitsign verify and gitsign verify-tag re-encode commit/tag objects through go-git's EncodeWithoutSignature before checking the signature, instead of verifying against the raw git object bytes. For malformed objects with duplicate tree headers, git-core and go-git parse different trees: git-core uses the first, go-git uses the second. A signature crafted over the go-git-normalized form (second tree) passes gitsign verify while git-core resolves the commit to a completely different tree. This breaks the invariant that a verified signature, the commit semantics git-core presents to users, and the object hash logged in Rekor all refer to the same content. This vulnerability is fixed in 0.16.0.

Record
EUVD-2026-30563
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-7rmh-48mx-2vwc 5.3

gitsign verify accepts signatures over go-git-normalized bytes, enabling trust confusion on malformed commits

Summary

gitsign verify and gitsign verify-tag re-encode commit/tag objects through go-git's EncodeWithoutSignature before checking the signature, instead of verifying against the raw git object bytes. For malformed objects with duplicate tree headers, git-core and go-git parse different trees: git-core uses the first, go-git uses the second. A signature crafted over the go-git-normalized form (second tree) passes gitsign verify while git-core resolves the commit to a completely different tree. This breaks the invariant that a verified signature, the commit semantics git-core presents to users, and the object hash logged in Rekor all refer to the same content.

Severity

Medium (CVSS 3.1: 5.7)

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N

  • Attack Vector: Network — a malformed commit can be distributed via any accessible git remote
  • Attack Complexity: High — exploitation requires crafting malformed objects that also bypass git server fsck checks (not universally enabled)
  • Privileges Required: None — the most impactful form (signature replay) requires no signing key
  • User Interaction: Required — a victim must run gitsign verify on the malformed commit
  • Scope: Unchanged — impact is confined to the repository under verification
  • Confidentiality Impact: None
  • Integrity Impact: High — a verified signature appears to endorse content different from what git-core resolves and presents to users
  • Availability Impact: None

Affected Component

  • internal/commands/verify/verify.go — (o *options).Run (line 75)
  • internal/commands/verify-tag/verify_tag.go — (o *options).Run (line 77)
  • pkg/git/verify.go — ObjectHash (lines 126–158, specifically the commit() round-trip at 161–176)

CWE

  • CWE-347: Improper Verification of Cryptographic Signature
  • CWE-295: Improper Certificate Validation (secondary — the mismatch allows a cert to appear to cover content it never covered)

Description

Root cause: re-encoding instead of raw-byte verification

When gitsign verify is invoked, the commit is opened via go-git and its body is reconstructed through EncodeWithoutSignature before being passed to the cryptographic verifier:

// internal/commands/verify/verify.go:63–92
c, err := repo.CommitObject(*h)          // go-git parses the raw object
...
c2 := new(plumbing.MemoryObject)
if err := c.EncodeWithoutSignature(c2); err != nil {  // re-encodes canonical form
    return err
}
r, _ := c2.Reader()
data, _ := io.ReadAll(r)

summary, err := v.Verify(ctx, data, sig, true)   // verifies re-encoded bytes, not raw bytes

The same pattern appears in verify-tag:

// internal/commands/verify-tag/verify_tag.go:76–95
tagData := new(plumbing.MemoryObject)
if err := tagObj.EncodeWithoutSignature(tagData); err != nil {
    return err
}

The loose-parsing assumption in go-git

The codebase itself acknowledges the problem in ObjectHash:

// pkg/git/verify.go:137–142
// We're making big assumptions here about the ordering of fields
// in Git objects. Unfortunately go-git does loose parsing of objects,
// so it will happily decode objects that don't match the unmarshal type.
// We should see if there's a better way to detect object types.
switch {
case bytes.HasPrefix(data, []byte("tree ")):
    encoder, err = commit(obj, sig)

go-git's loose parsing means that for a commit containing two tree headers, it silently discards the first and retains the second. EncodeWithoutSignature then produces a canonical commit body containing only the second tree — which can differ from what git-core resolves.

Divergent verification paths confirm the inconsistency

The git verify-commit path (internal/commands/root/verify.go) receives the raw commit bytes directly from git-core and does not re-encode them:

// internal/commands/root/verify.go:56–70
detached := len(args) >= 2
if detached {
   …
Record
GHSA-7rmh-48mx-2vwc
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
Weakness
CWE-295, CWE-347
Updated
2026-11-02
NVD 5.3

Gitsign is a keyless Sigstore to signing tool for Git commits with your a GitHub / OIDC identity. Prior to 0.16.0, gitsign verify and gitsign verify-tag re-encode commit/tag objects through go-git's EncodeWithoutSignature before checking the signature, instead of verifying against the raw git object bytes. For malformed objects with duplicate tree headers, git-core and go-git parse different trees: git-core uses the first, go-git uses the second. A signature crafted over the go-git-normalized form (second tree) passes gitsign verify while git-core resolves the commit to a completely different tree. This breaks the invariant that a verified signature, the commit semantics git-core presents to users, and the object hash logged in Rekor all refer to the same content. This vulnerability is fixed in 0.16.0.

Record
CVE-2026-44309
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
Weakness
CWE-295, CWE-347
Updated
2026-11-02
OSV 5.3

gitsign verify accepts signatures over go-git-normalized bytes, enabling trust confusion on malformed commits

Gitsign is a keyless Sigstore to signing tool for Git commits with your a GitHub / OIDC identity. Prior to 0.16.0, gitsign verify and gitsign verify-tag re-encode commit/tag objects through go-git's EncodeWithoutSignature before checking the signature, instead of verifying against the raw git object bytes. For malformed objects with duplicate tree headers, git-core and go-git parse different trees: git-core uses the first, go-git uses the second. A signature crafted over the go-git-normalized form (second tree) passes gitsign verify while git-core resolves the commit to a completely different tree. This breaks the invariant that a verified signature, the commit semantics git-core presents to users, and the object hash logged in Rekor all refer to the same content. This vulnerability is fixed in 0.16.0.

Record
CVE-2026-44309
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
Weakness
CWE-295, CWE-347
Updated
2026-11-02
OSVDEBIAN-CVE-2026-44309 5.3

Gitsign is a keyless Sigstore to signing tool for Git commits with your a GitHub / OIDC identity. Prior to 0.16.0, gitsign verify and gitsign verify-tag re-encode commit/tag objects through go-git's EncodeWithoutSignature before checking the signature, instead of verifying against the raw git object bytes. For malformed objects with duplicate tree headers, git-core and go-git parse different trees: git-core uses the first, go-git uses the second. A signature crafted over the go-git-normalized form (second tree) passes gitsign verify while git-core resolves the commit to a completely different tree. This breaks the invariant that a verified signature, the commit semantics git-core presents to users, and the object hash logged in Rekor all refer to the same content. This vulnerability is fixed in 0.16.0.

Record
DEBIAN-CVE-2026-44309
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
Updated
2026-11-02
Show 4 moreShow less
OSVGHSA-7rmh-48mx-2vwc 5.3

gitsign verify accepts signatures over go-git-normalized bytes, enabling trust confusion on malformed commits

Summary

gitsign verify and gitsign verify-tag re-encode commit/tag objects through go-git's EncodeWithoutSignature before checking the signature, instead of verifying against the raw git object bytes. For malformed objects with duplicate tree headers, git-core and go-git parse different trees: git-core uses the first, go-git uses the second. A signature crafted over the go-git-normalized form (second tree) passes gitsign verify while git-core resolves the commit to a completely different tree. This breaks the invariant that a verified signature, the commit semantics git-core presents to users, and the object hash logged in Rekor all refer to the same content.

Severity

Medium (CVSS 3.1: 5.7)

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N

  • Attack Vector: Network — a malformed commit can be distributed via any accessible git remote
  • Attack Complexity: High — exploitation requires crafting malformed objects that also bypass git server fsck checks (not universally enabled)
  • Privileges Required: None — the most impactful form (signature replay) requires no signing key
  • User Interaction: Required — a victim must run gitsign verify on the malformed commit
  • Scope: Unchanged — impact is confined to the repository under verification
  • Confidentiality Impact: None
  • Integrity Impact: High — a verified signature appears to endorse content different from what git-core resolves and presents to users
  • Availability Impact: None

Affected Component

  • internal/commands/verify/verify.go — (o *options).Run (line 75)
  • internal/commands/verify-tag/verify_tag.go — (o *options).Run (line 77)
  • pkg/git/verify.go — ObjectHash (lines 126–158, specifically the commit() round-trip at 161–176)

CWE

  • CWE-347: Improper Verification of Cryptographic Signature
  • CWE-295: Improper Certificate Validation (secondary — the mismatch allows a cert to appear to cover content it never covered)

Description

Root cause: re-encoding instead of raw-byte verification

When gitsign verify is invoked, the commit is opened via go-git and its body is reconstructed through EncodeWithoutSignature before being passed to the cryptographic verifier:

// internal/commands/verify/verify.go:63–92
c, err := repo.CommitObject(*h)          // go-git parses the raw object
...
c2 := new(plumbing.MemoryObject)
if err := c.EncodeWithoutSignature(c2); err != nil {  // re-encodes canonical form
    return err
}
r, _ := c2.Reader()
data, _ := io.ReadAll(r)

summary, err := v.Verify(ctx, data, sig, true)   // verifies re-encoded bytes, not raw bytes

The same pattern appears in verify-tag:

// internal/commands/verify-tag/verify_tag.go:76–95
tagData := new(plumbing.MemoryObject)
if err := tagObj.EncodeWithoutSignature(tagData); err != nil {
    return err
}

The loose-parsing assumption in go-git

The codebase itself acknowledges the problem in ObjectHash:

// pkg/git/verify.go:137–142
// We're making big assumptions here about the ordering of fields
// in Git objects. Unfortunately go-git does loose parsing of objects,
// so it will happily decode objects that don't match the unmarshal type.
// We should see if there's a better way to detect object types.
switch {
case bytes.HasPrefix(data, []byte("tree ")):
    encoder, err = commit(obj, sig)

go-git's loose parsing means that for a commit containing two tree headers, it silently discards the first and retains the second. EncodeWithoutSignature then produces a canonical commit body containing only the second tree — which can differ from what git-core resolves.

Divergent verification paths confirm the inconsistency

The git verify-commit path (internal/commands/root/verify.go) receives the raw commit bytes directly from git-core and does not re-encode them:

// internal/commands/root/verify.go:56–70
detached := len(args) >= 2
if detached {
   …
Record
GHSA-7rmh-48mx-2vwc
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
Weakness
CWE-295, CWE-347
Updated
2026-11-02
OSVUBUNTU-CVE-2026-44309 5.3

Gitsign is a keyless Sigstore to signing tool for Git commits with your a GitHub / OIDC identity. Prior to 0.16.0, gitsign verify and gitsign verify-tag re-encode commit/tag objects through go-git's EncodeWithoutSignature before checking the signature, instead of verifying against the raw git object bytes. For malformed objects with duplicate tree headers, git-core and go-git parse different trees: git-core uses the first, go-git uses the second. A signature crafted over the go-git-normalized form (second tree) passes gitsign verify while git-core resolves the commit to a completely different tree. This breaks the invariant that a verified signature, the commit semantics git-core presents to users, and the object hash logged in Rekor all refer to the same content. This vulnerability is fixed in 0.16.0.

Record
UBUNTU-CVE-2026-44309
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
Updated
2026-11-02
OSVGO-2026-5233 No score

gitsign verify accepts signatures over go-git-normalized bytes, enabling trust confusion on malformed commits in github.com/sigstore/gitsign

gitsign verify accepts signatures over go-git-normalized bytes, enabling trust confusion on malformed commits in github.com/sigstore/gitsign

Record
GO-2026-5233
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/sigstore/gitsign
Go
 before 0.16.0
0.16.0
gitsign
Debian:13
 All versions, plus listed versions
0.13.0-20.13.0-30.13.0-40.13.0-4~exp00.14.0-1
Show 6 moreShow less
0.14.0-1~exp00.16.0-10.16.1-10.16.1-20.16.1-2~exp00.16.1-3
 None known
gitsign
Debian:14
 before 0.16.0-1, plus listed versions
0.13.0-20.13.0-30.13.0-40.13.0-4~exp00.14.0-10.14.0-1~exp0
0.16.0-1
gitsign
Ubuntu:25.10
 All versions, plus listed versions
0.12.0-40.13.0-10.13.0-2
 None known
gitsign
Ubuntu:26.10
 All versions, plus listed versions
0.13.0-40.16.1-20.16.1-3
 None known
gitsign
Ubuntu:Pro:26.04:LTS
 All versions, plus listed versions
0.13.0-20.13.0-30.13.0-40.13.0-4ubuntu0.26.04.1~esm1
 None known
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-44309 is a medium vulnerability (CVSS 5.3) in Sigstore Gitsign, published May 8, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.14%, the 3rd percentile. Fixed in github.com/sigstore/gitsign 0.16.0.

References

Show 194 moreShow less
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Left out here: 1,542 references and the rest of 3 source descriptions. The JSON record has them.

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