{"id":"CVE-2026-47734","aliases":["GHSA-xrvj-v92f-53gj","PYSEC-2026-2466"],"url":"https://o3.security/vulnerability/CVE-2026-47734","summary":"Dulwich has unbounded memory allocation in receive-pack from crafted thin packs","details":"## Impact\n\nAn uncontrolled-resource-consumption (memory exhaustion) denial-of-service vulnerability (CWE-400 / CWE-789).\n\nA client with push access could push a tiny crafted thin pack (~174 bytes)  whose delta header declares a huge   dest_size. When dulwich ingested it via  add_thin_pack / apply_delta, it would  allocate hundreds of MB of memory based on that attacker-controlled size, with no relationship to the actual bytes received.\n\nWho is impacted: Operators running a Dulwich-based Git server that exposes git-receive-pack (i.e. accepts pushes) -\nfor example via dulwich.server functionality, the HTTP  smart server, or anything built on ReceivePackHandler. \n\n## Patches\n\nPatched in 1.2.5.\n\nadd_thin_pack now accepts a max_input_size keyword (bytes; 0/None = unlimited, matching git's semantics), and ReceivePackHandler reads receive.maxInputSize from the repository config and passes it through. Wire reads are counted and a PackInputTooLarge exception is raised once the cap is exceeded - equivalent to git index-pack --max-input-size.\n\nUsers should upgrade to Dulwich 1.2.5 or later and set receive.maxInputSize in their server's repository config to a sane bound for their environment.\n\n## Workarounds\n\nOn unpatched versions, receive.maxInputSize has no effect, so it cannot be used as a workaround. Until upgrading, operators should:\n\n- Restrict dulwich-receive-pack (push) access to trusted, authenticated clients only, or disable it entirely on servers that only need to serve fetches.\n- Run the server under an OS-level memory limit (e.g. ulimit, cgroups/MemoryMax, or a container memory limit) so a malicious push is killed rather than taking down the host.\n\n##  Resources\n\n- git's receive.maxInputSize / git index-pack --max-input-size documentation \n- Reported by Liyi, Ziyue, Strick, Maurice and Chenchen @ University of Sydney","published":"2026-06-10T22:11:02.704Z","modified":"2026-10-21T02:59:14.667883323Z","cvss":{"score":5.7,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H"},"epss":{"score":0.00188,"percentile":0.08766,"asOf":"2026-08-20"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"dulwich","fixedVersion":"1.2.5"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/47xxx/CVE-2026-47734.json"},{"type":"ADVISORY","url":"https://github.com/jelmer/dulwich/security/advisories/GHSA-xrvj-v92f-53gj"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47734"},{"type":"PACKAGE","url":"https://github.com/jelmer/dulwich"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:59:14.667883323Z"}}