CVE-2026-57886

Cross-repository issue/comment attachment re-linking can expose private attachment content

Cross-repository issue/comment attachment re-linking can expose private attachment content

Summary

Gitea's issue and comment attachment update paths accept attachment UUIDs without verifying that each attachment belongs to the target issue/comment repository. If an authenticated attacker knows a victim attachment UUID, they can re-link that attachment to an attacker-controlled issue or comment, causing later attachment access checks to use the attacker's repository authorization context.

Affected

• Component: web issue/comment attachment handling.
• Confirmed version: main commit a39b2775edcb3ba53def96794491b91335117d81 (v1.27.0-dev-352-ga39b2775ed).
• Fixed in: not fixed at the time of validation.
• Other versions: not exhaustively tested. The affected code path appears structurally similar to versions that contain the current issue/comment attachment update logic.

Description / Root Cause

files[] values from issue/comment edit flows are passed to updateAttachments in routers/web/repo/issue.go:589-629. That helper calls:

• models/issues/issue_update.go:267-278 (UpdateIssueAttachments)
• models/issues/comment.go:623-642 (UpdateCommentAttachments)

Both functions load attachments by UUID and update the attachment linkage, but neither validates that the attachment row's RepoID matches the repository of the target issue/comment. They also do not reject attachments already linked to a different issue/comment.

Attachment reads then use the linked issue/release repository to decide access:

• services/repository/repository.go:185-207 returns the repository ID from IssueID or ReleaseID.
• routers/web/repo/attachment.go:153-184 checks read permission on that linked repository.
• routers/web/repo/attachment.go:216-224 opens and serves the file from the attachment's storage path after the linked-repository permission check succeeds.

For the global /attachments/{uuid} route in routers/web/web.go:872-876, there is no current repository context, so the early attach.RepoID mismatch check in ServeAttachment does not protect against this re-linking case.

A patched sibling path already demonstrates the intended invariant: models/repo/release.go:179-215 rejects release attachments whose RepoID differs from the release repository. That guard was introduced for CVE-2026-20736, but the issue/comment paths still lack an equivalent check.

Impact

An attacker who can edit an issue/comment in a repository they can read can move a known victim attachment UUID into that repository's authorization context. After the re-link, the attachment download path resolves access against the attacker-controlled repository while serving the original attachment file.

This can disclose private issue/comment attachments if the attacker has obtained the UUID through prior legitimate access, copied links, notification content, logs, browser history, or another exposure. The attack does not require write access to the victim repository.

Reproduction Summary

Full HTTP/E2E observation:

• A local Gitea server was started with an isolated SQLite database.
• A victim user created private repositories, private issues, and issue attachments containing unique marker strings.
• An attacker user first attempted to download each victim attachment through /attachments/{uuid} and received 404.
• The attacker then submitted the victim UUID through the real issue edit route in an attacker-controlled public repository.
• The same attacker could then download the victim issue attachment through /attachments/{uuid} and received 200; the response body contained the unique issue marker.
• The attacker repeated the flow through the real comment edit route and could download the second victim attachment with 200; the response body contained the unique comment marker.

Model-level issue-path behavior:

• A fixture attachment with RepoID = 2 and IssueID = 4 was passed to UpdateIssueAttachments for attacker issue ID = 1, whose RepoID = 1.
• The call succeeded.
• The attachment row still had…

Cross-repository issue/comment attachment re-linking can expose private attachment content

Cross-repository issue/comment attachment re-linking can expose private attachment content

Summary

Gitea's issue and comment attachment update paths accept attachment UUIDs without verifying that each attachment belongs to the target issue/comment repository. If an authenticated attacker knows a victim attachment UUID, they can re-link that attachment to an attacker-controlled issue or comment, causing later attachment access checks to use the attacker's repository authorization context.

Affected

• Component: web issue/comment attachment handling.
• Confirmed version: main commit a39b2775edcb3ba53def96794491b91335117d81 (v1.27.0-dev-352-ga39b2775ed).
• Fixed in: not fixed at the time of validation.
• Other versions: not exhaustively tested. The affected code path appears structurally similar to versions that contain the current issue/comment attachment update logic.

Description / Root Cause

files[] values from issue/comment edit flows are passed to updateAttachments in routers/web/repo/issue.go:589-629. That helper calls:

• models/issues/issue_update.go:267-278 (UpdateIssueAttachments)
• models/issues/comment.go:623-642 (UpdateCommentAttachments)

Both functions load attachments by UUID and update the attachment linkage, but neither validates that the attachment row's RepoID matches the repository of the target issue/comment. They also do not reject attachments already linked to a different issue/comment.

Attachment reads then use the linked issue/release repository to decide access:

• services/repository/repository.go:185-207 returns the repository ID from IssueID or ReleaseID.
• routers/web/repo/attachment.go:153-184 checks read permission on that linked repository.
• routers/web/repo/attachment.go:216-224 opens and serves the file from the attachment's storage path after the linked-repository permission check succeeds.

For the global /attachments/{uuid} route in routers/web/web.go:872-876, there is no current repository context, so the early attach.RepoID mismatch check in ServeAttachment does not protect against this re-linking case.

A patched sibling path already demonstrates the intended invariant: models/repo/release.go:179-215 rejects release attachments whose RepoID differs from the release repository. That guard was introduced for CVE-2026-20736, but the issue/comment paths still lack an equivalent check.

Impact

An attacker who can edit an issue/comment in a repository they can read can move a known victim attachment UUID into that repository's authorization context. After the re-link, the attachment download path resolves access against the attacker-controlled repository while serving the original attachment file.

This can disclose private issue/comment attachments if the attacker has obtained the UUID through prior legitimate access, copied links, notification content, logs, browser history, or another exposure. The attack does not require write access to the victim repository.

Reproduction Summary

Full HTTP/E2E observation:

• A local Gitea server was started with an isolated SQLite database.
• A victim user created private repositories, private issues, and issue attachments containing unique marker strings.
• An attacker user first attempted to download each victim attachment through /attachments/{uuid} and received 404.
• The attacker then submitted the victim UUID through the real issue edit route in an attacker-controlled public repository.
• The same attacker could then download the victim issue attachment through /attachments/{uuid} and received 200; the response body contained the unique issue marker.
• The attacker repeated the flow through the real comment edit route and could download the second victim attachment with 200; the response body contained the unique comment marker.

Model-level issue-path behavior:

• A fixture attachment with RepoID = 2 and IssueID = 4 was passed to UpdateIssueAttachments for attacker issue ID = 1, whose RepoID = 1.
• The call succeeded.
• The attachment row still had…

Gitea: Cross-repository issue/comment attachment re-linking can expose private attachment content in gitea.dev

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 *…