vulnerability / NVI-00013198 / Revision 1
Dulwich: Infinite Loop Denial of Service (DoS) in Packfile Object Resolution
GitHub lists this reviewed advisory for dulwich. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
6.5 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
dulwich
source listed< 1.2.9
### Affected file * `dulwich/pack.py` (Method: `Pack.resolve_object`) ### Description / Summary A High-severity Denial of Service (DoS) vulnerability exists in the `Pack.resolve_object` method. When resolving an `OFS_DELTA` object, the resolver calculates the base offset using `base_offset = obj_offset - delta_offset`. If a malicious packfile contains an `OFS_DELTA` object where `delta_offset` is `0`, the calculation `obj_offset - 0` resolves back to the current object's own offset. Because the implementation lacks a depth counter, a "visited" set, or an explicit rejection of `delta_offset == 0`, the resolver enters an infinite recursive loop, exhausting CPU resources and eventually crashing the process. **Vulnerable Code Breakdown (`dulwich/pack.py`):** ```python elif obj_type == OFS_DELTA: delta_offset = parse_pack_object_offset_at(...) base_offset = obj_offset - delta_offset # VULNERABILITY: Self-reference if delta_offset == 0 base_type, base_data = self.resolve_object(...) # VULNERABILITY: Infinite recursion ``` ### Potential impact An attacker can trigger this infinite loop via any operation that walks packfiles (e.g., `dulwich clone`, `fetch`, `cat-
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-35mr-4567-66vg ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.