GHSA-9hx2-hgq2-2g4f BIT-pillow-2021-25292 CVE-2021-25292 PYSEC-2021-38
Regular Expression Denial of Service (ReDoS) in Pillow
Medium
PyPI
- Severity
- 0.0 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 1.73%
- Chance of exploitation in the next 30 days. Higher than 77.57% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-400 Uncontrolled Resource Consumption
- Fix
8.1.1- Upgrade pillow to this version or later
Description
An issue was discovered in Pillow before 8.1.1. The PDF parser allows a regular expression DoS (ReDoS) attack via a crafted PDF file because of a catastrophic backtracking regex.
Affected versions
PyPI
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
pillow PyPI → 8.1.1
- pip
pip install --upgrade "pillow>=8.1.1"- poetry
poetry add "pillow>=8.1.1"- uv
uv add "pillow>=8.1.1"
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- None
- User interaction
- Active
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- High
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
CVSS 3.1 6.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
CWE-400: Uncontrolled Resource Consumption
The product does not properly control the allocation and maintenance of a limited resource.
How to prevent it
- Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
- Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question. The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
- Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
- Implementation: Ensure that all failures in resource allocation place the system into a safe posture.
References
Advisories
Other links
- github.com/python-pillow/Pillow/commit/3bce145966374dd39ce58a6fc0083f8d1890719c
- github.com/python-pillow/Pillow/commit/521dab94c7ab72b037bd9a83e9663401e0fd2cee
- github.com/python-pillow/Pillow/commit/6207b44ab1ff4a91d8ddc7579619876d0bb191a4
- github.com/pypa/advisory-database/tree/main/vulns/pillow/PYSEC-2021-38.yaml
- github.com/python-pillow/Pillow
- pillow.readthedocs.io/en/stable/releasenotes/8.1.1.html
- security.gentoo.org/glsa/202107-33
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| PYSEC-2023-175 Pillow versions before v10.0.1 bundled libwebp binaries in wheels that are vulnerable to CVE-2023-5129 (previously CVE-2023-4863). | High Known exploited | Also affects pillow |
| GHSA-j7hp-h8jx-5ppr libwebp: OOB write in BuildHuffmanTable | High Known exploited | Also affects pillow |
| GHSA-78g4-xqwv-q3g8 Pillow: Bundled libopenjp2 2.5.4 in all wheels since 11.1.0 carries OSV-2025-219 heap-buffer-overflow write reachable from Image.open().load() | High | Also affects pillow |
| GHSA-654x-cwwv-5j9c Pillow: Arrow export leaks stale heap memory when PILLOW_ALIGNMENT > 1 | Medium | Also affects pillow |
| GHSA-xvh5-g6gv-559v Pillow: Memory disclosure and segfault in libtiff encoder via crafted TIFF tags | High | Also affects pillow |
| GHSA-g7cr-3p24-7wf7 Pillow: Heap buffer overflow writing JPEG comment after ICC profile fills buffer | High | Also affects pillow |
| GHSA-9v9v-9qvf-h2hj Pillow: Heap over-read in WMF/EMF rendering via 16-bit dimension truncation (Windows builds) | High | Also affects pillow |
| GHSA-g4qv-2jxx-769h Pillow: PNG eXIf chunk makes EXIF parsing run in quadratic time | Medium | Also affects pillow |
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