vulnerability / NVI-00010631 / Revision 3
Pillow: Decompression bomb check bypass in SpiderImagePlugin.seek() leads to unbounded allocation DoS
GitHub lists this reviewed advisory for pillow. 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.
0.373%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.3126. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
pillow
source listed< 13.0.0
## Summary SpiderImagePlugin's seek() bypasses the decompression bomb check, allowing a tiny (<1KB) crafted SPIDER stack file to trigger a multi-gigabyte allocation on im.load(). ## Affected versions All versions up to and including current HEAD (v13.0.0.dev0, commit e7a7ea84) ## Root cause Image.open() runs Image._decompression_bomb_check(im.size) exactly once, in _open_core (src/PIL/Image.py:3668), right after the initial _open(). SPIDER stack files are multi-frame: SpiderImageFile.seek(frame) (SpiderImagePlugin.py:179-190) computes an attacker-influenced stkoffset and calls self._open() AGAIN directly (line 190) — NOT through Image.open(). _open() re-parses a fresh 27-float header at that offset and reassigns: self._size = int(h[12]), int(h[2]) # SpiderImagePlugin.py:131 straight from unvalidated header floats (isSpiderHeader only checks internal labrec*lenbyt==labbyt consistency, never bounds nsam/nrow). No bomb check runs on this new size. On the subsequent load(), ImageFile.load_prepare() (ImageFile.py:436-437) executes `self.im = Image.core.new(self.mode, self.size)` with the unchecked, attacker-chosen size. Mode is always "F" (4 bytes/pixel), so e.g. 40000x4
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. FIRST EPSS
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-g842-9rc4-69pw ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-96637 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 3 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.