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CVE-2026-20779

Gitea TOTP single-use enforcement defect allows OTP replay

7.1 HighFix available

Gitea versions from 1.5.0 before 1.26.3 have a TOTP single-use enforcement defect that allows a valid TOTP code to be accepted more than once across web two-factor authentication flows and the Basic Auth X-Gitea-OTP path.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
High
Integrity
Low
Availability
None

Exploit likelihood

0.49%Unchanged since Jul 4, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.1

Gitea TOTP single-use enforcement defect allows OTP replay

Gitea versions from 1.5.0 before 1.26.3 have a TOTP single-use enforcement defect that allows a valid TOTP code to be accepted more than once across web two-factor authentication flows and the Basic Auth X-Gitea-OTP path.

Record
CVE-2026-20779
CVSS 3.1
7.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
Weakness
CWE-294
Updated
2026-11-02
EUVDEUVD-2026-41613 7.1

Gitea versions from 1.5.0 before 1.26.3 have a TOTP single-use enforcement defect that allows a valid TOTP code to be accepted more than once across web two-factor authentication flows and the Basic Auth X-Gitea-OTP path.

Record
EUVD-2026-41613
CVSS 3.1
7.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-gx3v-q759-g323 7.1

Gitea: TOTP TOCTOU race on web 2FA paths + missing replay check on Basic-Auth `X-Gitea-OTP` surface

Summary

I'm reporting two related TOTP one-time-use defects in Gitea that survive the CVE-2021-45331 fix. The 2018 fix (PR #3878) introduced the TwoFactor.LastUsedPasscode field and added an in-memory inequality check on the web 2FA login path. That check works correctly in the single-request case, but it leaves two follow-up gaps:

  1. A TOCTOU race on the web surfaces (Defect 1). The read-validate-check-save sequence against the two_factor row is not atomic. Two parallel submissions of the same passcode each load their own in-memory copy where LastUsedPasscode still holds the prior value; both pass the inequality check, both authenticate, and both then write the same new value back. Net effect: the same OTP redeems for two independent logged-in sessions.

  2. No LastUsedPasscode check at all on the Basic-Auth API surface (Defect 2). services/auth/basic.go calls twofa.ValidateTOTP(...) for X-Gitea-OTP without ever reading or writing LastUsedPasscode. The same six-digit code is replayable for the full totp.Validate acceptance window (~60–90 s with the default Skew=1). This is a clean RFC 6238 §5.2 violation independent of timing, shaped identically to the pre-CVE-2021-45331 behaviour but scoped to the API / Git-over-HTTPS basic-auth path instead of the web form.

Both defects post-date the 2018 fix; neither is referenced in any published Gitea advisory I could find. I'm filing this as a follow-up to CVE-2021-45331, not a duplicate.

Vulnerable code

Defect 1 — TOCTOU race on web 2FA login

routers/web/auth/2fa.go:55-88:

54  id := idSess.(int64)
55  twofa, err := auth.GetTwoFactorByUID(ctx, id)             // (A) read row
56  ...
62  ok, err := twofa.ValidateTOTP(form.Passcode)              // (B) pure-function RFC 6238 check
...
68  if ok && twofa.LastUsedPasscode != form.Passcode {        // (C) check against in-memory copy
...
84      twofa.LastUsedPasscode = form.Passcode                 // (D) mutate in-memory
85      if err = auth.UpdateTwoFactor(ctx, twofa); err != nil {// (E) UPDATE … AllCols where id=?

Step (E) is plain db.GetEngine(ctx).ID(t.ID).AllCols().Update(t) (models/auth/twofactor.go:128-131) — no row lock, no WHERE last_used_passcode = <previous> predicate, and no DB uniqueness on (uid, last_used_passcode). The model definition at models/auth/twofactor.go:48-57 shows LastUsedPasscode string is a plain column — no constraint, no version field.

Defect 1 — same shape, password-reset 2FA re-auth

routers/web/auth/password.go:179-196 shows the identical pattern in the password-reset flow:

179  passcode := ctx.FormString("passcode")
180  ok, err := twofa.ValidateTOTP(passcode)
...
185  if !ok || twofa.LastUsedPasscode == passcode {           // same check-against-in-memory pattern
...
192  twofa.LastUsedPasscode = passcode
193  if err = auth.UpdateTwoFactor(ctx, twofa); err != nil {

Same shape, same race window.

Defect 2 — Basic-Auth API / Git-over-HTTPS (stateless replay — no check at all)

services/auth/basic.go:170-185:

func validateTOTP(req *http.Request, u *user_model.User) error {
    twofa, err := auth_model.GetTwoFactorByUID(req.Context(), u.ID)
    ...
    if ok, err := twofa.ValidateTOTP(req.Header.Get("X-Gitea-OTP")); err != nil {  // :179
        return err
    } else if !ok {
        return util.NewInvalidArgumentErrorf("invalid provided OTP")
    }
    return nil
}

LastUsedPasscode is neither read nor written on this path. The same six-digit code in X-Gitea-OTP succeeds for the full totp.Validate acceptance window on every request.

Why the existing failed-login counter doesn't catch either defect

Gitea's loginAttempts counter increments on failed sign-ins. A successful replay is a success — the counter is never touched, and two parallel successes produce two access tokens with no anomaly…

Record
GHSA-gx3v-q759-g323
CVSS 3.1
7.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
Weakness
CWE-294
Updated
2026-11-02
NVD 7.1

Gitea versions from 1.5.0 before 1.26.3 have a TOTP single-use enforcement defect that allows a valid TOTP code to be accepted more than once across web two-factor authentication flows and the Basic Auth X-Gitea-OTP path.

Record
CVE-2026-20779
CVSS 3.1
7.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
Weakness
CWE-294
Updated
2026-11-02
OSV 7.1

Gitea TOTP single-use enforcement defect allows OTP replay

Gitea versions from 1.5.0 before 1.26.3 have a TOTP single-use enforcement defect that allows a valid TOTP code to be accepted more than once across web two-factor authentication flows and the Basic Auth X-Gitea-OTP path.

Record
CVE-2026-20779
CVSS 3.1
7.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
Weakness
CWE-294
Updated
2026-11-02
OSVGHSA-gx3v-q759-g323 7.1

Gitea: TOTP TOCTOU race on web 2FA paths + missing replay check on Basic-Auth `X-Gitea-OTP` surface

Summary

I'm reporting two related TOTP one-time-use defects in Gitea that survive the CVE-2021-45331 fix. The 2018 fix (PR #3878) introduced the TwoFactor.LastUsedPasscode field and added an in-memory inequality check on the web 2FA login path. That check works correctly in the single-request case, but it leaves two follow-up gaps:

  1. A TOCTOU race on the web surfaces (Defect 1). The read-validate-check-save sequence against the two_factor row is not atomic. Two parallel submissions of the same passcode each load their own in-memory copy where LastUsedPasscode still holds the prior value; both pass the inequality check, both authenticate, and both then write the same new value back. Net effect: the same OTP redeems for two independent logged-in sessions.

  2. No LastUsedPasscode check at all on the Basic-Auth API surface (Defect 2). services/auth/basic.go calls twofa.ValidateTOTP(...) for X-Gitea-OTP without ever reading or writing LastUsedPasscode. The same six-digit code is replayable for the full totp.Validate acceptance window (~60–90 s with the default Skew=1). This is a clean RFC 6238 §5.2 violation independent of timing, shaped identically to the pre-CVE-2021-45331 behaviour but scoped to the API / Git-over-HTTPS basic-auth path instead of the web form.

Both defects post-date the 2018 fix; neither is referenced in any published Gitea advisory I could find. I'm filing this as a follow-up to CVE-2021-45331, not a duplicate.

Vulnerable code

Defect 1 — TOCTOU race on web 2FA login

routers/web/auth/2fa.go:55-88:

54  id := idSess.(int64)
55  twofa, err := auth.GetTwoFactorByUID(ctx, id)             // (A) read row
56  ...
62  ok, err := twofa.ValidateTOTP(form.Passcode)              // (B) pure-function RFC 6238 check
...
68  if ok && twofa.LastUsedPasscode != form.Passcode {        // (C) check against in-memory copy
...
84      twofa.LastUsedPasscode = form.Passcode                 // (D) mutate in-memory
85      if err = auth.UpdateTwoFactor(ctx, twofa); err != nil {// (E) UPDATE … AllCols where id=?

Step (E) is plain db.GetEngine(ctx).ID(t.ID).AllCols().Update(t) (models/auth/twofactor.go:128-131) — no row lock, no WHERE last_used_passcode = <previous> predicate, and no DB uniqueness on (uid, last_used_passcode). The model definition at models/auth/twofactor.go:48-57 shows LastUsedPasscode string is a plain column — no constraint, no version field.

Defect 1 — same shape, password-reset 2FA re-auth

routers/web/auth/password.go:179-196 shows the identical pattern in the password-reset flow:

179  passcode := ctx.FormString("passcode")
180  ok, err := twofa.ValidateTOTP(passcode)
...
185  if !ok || twofa.LastUsedPasscode == passcode {           // same check-against-in-memory pattern
...
192  twofa.LastUsedPasscode = passcode
193  if err = auth.UpdateTwoFactor(ctx, twofa); err != nil {

Same shape, same race window.

Defect 2 — Basic-Auth API / Git-over-HTTPS (stateless replay — no check at all)

services/auth/basic.go:170-185:

func validateTOTP(req *http.Request, u *user_model.User) error {
    twofa, err := auth_model.GetTwoFactorByUID(req.Context(), u.ID)
    ...
    if ok, err := twofa.ValidateTOTP(req.Header.Get("X-Gitea-OTP")); err != nil {  // :179
        return err
    } else if !ok {
        return util.NewInvalidArgumentErrorf("invalid provided OTP")
    }
    return nil
}

LastUsedPasscode is neither read nor written on this path. The same six-digit code in X-Gitea-OTP succeeds for the full totp.Validate acceptance window on every request.

Why the existing failed-login counter doesn't catch either defect

Gitea's loginAttempts counter increments on failed sign-ins. A successful replay is a success — the counter is never touched, and two parallel successes produce two access tokens with no anomaly…

Record
GHSA-gx3v-q759-g323
CVSS 3.1
7.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
Weakness
CWE-294
Updated
2026-11-02
OSVGO-2026-6057 No score

Gitea: TOTP TOCTOU race on web 2FA paths + missing replay check on Basic-Auth `X-Gitea-OTP` surface in code.gitea.io/gitea

Gitea: TOTP TOCTOU race on web 2FA paths + missing replay check on Basic-Auth X-Gitea-OTP surface in code.gitea.io/gitea

Record
GO-2026-6057
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
code.gitea.io/gitea
Go
 1.5.0 up to 1.26.3
1.26.3
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
aliases, publishedEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

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

In short

CVE-2026-20779 is a high vulnerability (CVSS 7.1) in Gitea Open Source Git Server, published July 3, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.49%, the 42nd percentile. Fixed in code.gitea.io/gitea 1.26.3.

References

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