Dulwich EUVD-2026-106898

Exploitation requires that a victim perform a packfile-walking operation - dulwich clone, fetch, cat-file, or any internal Pack.__getitem__/Pack.resolve_object lookup - against an attacker-supplied packfile containing an OFS_DELTA object whose delta_offset field is exactly 0 (causing base_offset = obj_offset - 0 to self-reference). No authentication is required (PR:N), but the attack is gated by passive user interaction (UI:P): the attacker cannot trigger it unsolicited and must induce the victim/service to process the malicious pack. The primary limiting factor is therefore that the target must ingest attacker-controlled packfiles - highest real-world exposure is for multi-tenant or internet-facing services (CI/CD runners, Git hosting/web frontends) built on dulwich < 1.2.9; isolated clients cloning only trusted repositories are at low practical risk. Fixed in 1.2.9.

This is a credible but moderate-priority denial-of-service issue, not a critical system-compromise flaw. The provided CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H) scores 7.1 and correctly reflects a network-reachable, low-complexity, unauthenticated attack whose only impact is availability (VA:H) - there is no confidentiality or integrity loss (VC:N/VI:N), consistent with CWE-835 (infinite loop/recursion). The key moderating signal is UI:P (passive user interaction): exploitation requires a victim to initiate a packfile-walking operation (clone, fetch, cat-file) against attacker-supplied data, so this is not a wormable, self-propagating remote exploit. Publicly available exploit code exists (a 44-byte PoC packfile is published in the GHSA advisory), which raises practical risk, but this is NOT the same as active exploitation. The CVE is NOT in CISA KEV, and no EPSS score was provided in the input, so exploitation probability cannot be quantified from this data. Net: a real, easily reproducible DoS against any service that parses untrusted packfiles (CI/CD runners, Git web frontends built on dulwich), but bounded to availability and gated by the victim-initiated-operation requirement - prioritize patching for internet-facing or multi-tenant dulwich-backed services over isolated client use.

An attacker hosts a malicious Git repository (or submits a crafted packfile to a service that ingests them) containing a single OFS_DELTA object whose delta_offset is 0, making the object reference its own offset. When a victim service or user runs clone, fetch, or cat-file against it, dulwich's Pack.resolve_object recurses into itself endlessly, pinning a CPU core at 100% and hanging or crashing the process. A working proof-of-concept that generates the 44-byte trigger packfile is published in the vendor advisory.