{"id":"CVE-2026-47734","aliases":["GHSA-xrvj-v92f-53gj"],"title":"Dulwich has unbounded memory allocation in receive-pack from crafted thin packs","summary":"Dulwich has unbounded memory allocation in receive-pack from crafted thin packs","severity":"medium","cvss":5.7,"cwe":["CWE-400","CWE-789"],"vendor":"dulwich","product":"dulwich","ecosystem":"pip","affected":["dulwich >= 0.1.0, < 1.2.5"],"patched":["dulwich 1.2.5"],"published":"2026-06-08","updated":"2026-06-11","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-xrvj-v92f-53gj","references":[{"url":"https://github.com/jelmer/dulwich/security/advisories/GHSA-xrvj-v92f-53gj"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47734"},{"url":"https://github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5"},{"url":"https://github.com/advisories/GHSA-xrvj-v92f-53gj"}],"tags":["ghsa","pip"],"epss":0.00188,"epssPercentile":0.08656,"ingestedAt":"2026-07-07T15:41:59.614Z","slug":"CVE-2026-47734","body":"## Overview\n\n## 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\n\n## Affected packages\n\n- `dulwich >= 0.1.0, < 1.2.5`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `dulwich 1.2.5`","depth":"sunlit","depthScore":31,"depthScoreParts":{"impact":31.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}