If the value passed to os.path.expandvars() is user-controlled a performance degradation is possible when expanding environment variables.
Weakness
The product does not properly control the allocation and maintenance of a limited resource.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Red Hat Enterprise Linux 8 | RedHat | python39:3.9-8100020251126112422.d47b87a4 | * |
| Red Hat Enterprise Linux 8 | RedHat | python39-devel:3.9-8100020251126112422.d47b87a4 | * |
| Red Hat Enterprise Linux 9 | RedHat | python3.9-0:3.9.25-2.el9_7 | * |
| Red Hat Enterprise Linux 9 | RedHat | python3.9-0:3.9.25-2.el9_7 | * |
| Red Hat Discovery 2 | RedHat | discovery/discovery-server-rhel9:sha256:d4e8987a100ea60942306f1564679e51fa1364f6124fbfb3100959f83a1f16bf | * |
| Red Hat Discovery 2 | RedHat | discovery/discovery-ui-rhel9:sha256:899bd7f941512d54af8ab369ca03028a7d27d05887ccce24bc12c7ccd3e4dbee | * |
| Red Hat Update Infrastructure 5 | RedHat | rhui5/cds-rhel9:sha256:87d268fd03fa0063620a043b43bce078144e06849ca6b83fd0e375c13ecb15be | * |
| Red Hat Update Infrastructure 5 | RedHat | rhui5/haproxy-rhel9:sha256:c0cb48d44556c064626eab0d70e5f427ac132bbd921342dcb862267413bf8d16 | * |
| Red Hat Update Infrastructure 5 | RedHat | rhui5/installer-rhel9:sha256:e1d64fbd0e4b90259d9fbb94736ed74c7c384d13067c6bbbb107c664683cb1a9 | * |
| Red Hat Update Infrastructure 5 | RedHat | rhui5/rhua-rhel9:sha256:4642951a6a57511f8b481a6481fcd417fc7f3de86511cdab28b9b89639c2bdb2 | * |
| Pypy3 | Ubuntu | plucky | * |
| Python3.10 | Ubuntu | jammy | * |
| Python3.11 | Ubuntu | esm-apps/jammy | * |
| Python3.11 | Ubuntu | jammy | * |
| Python3.12 | Ubuntu | noble | * |
| Python3.13 | Ubuntu | plucky | * |
| Python3.13 | Ubuntu | upstream | * |
| Python3.14 | Ubuntu | upstream | * |
| Python3.4 | Ubuntu | esm-infra-legacy/trusty | * |
| Python3.5 | Ubuntu | esm-infra-legacy/trusty | * |
| Python3.5 | Ubuntu | esm-infra/xenial | * |
| Python3.6 | Ubuntu | esm-infra/bionic | * |
| Python3.7 | Ubuntu | esm-apps/bionic | * |
| Python3.8 | Ubuntu | esm-apps/bionic | * |
| Python3.8 | Ubuntu | esm-infra/focal | * |
| Python3.9 | Ubuntu | esm-apps/focal | * |
Potential Mitigations
Mitigation of resource exhaustion attacks requires that the target system either:
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.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/147.html
- https://cwe.mitre.org/data/definitions/227.html
- https://cwe.mitre.org/data/definitions/492.html
References
- https://github.com/python/cpython/commit/2e6150adccaaf5bd95d4c19dfd04a36e0b325d8c
- https://github.com/python/cpython/commit/5dceb93486176e6b4a6d9754491005113eb23427
- https://github.com/python/cpython/commit/631ba3407e3348ccd56ce5160c4fb2c5dc5f4d84
- https://github.com/python/cpython/commit/892747b4cf0f95ba8beb51c0d0658bfaa381ebca
- https://github.com/python/cpython/commit/9ab89c026aa9611c4b0b67c288b8303a480fe742
- https://github.com/python/cpython/commit/c8a5f3435c342964e0a432cc9fb448b7dbecd1ba
- https://github.com/python/cpython/commit/f029e8db626ddc6e3a3beea4eff511a71aaceb5c
- https://github.com/python/cpython/issues/136065
- https://mail.python.org/archives/list/security-announce@python.org/thread/IUP5QJ6D4KK6ULHOMPC7DPNKRYQTQNLA/