VulnerabilityPublished 29 Oct 2026

CVE-2026-113723: virtualenv · Bash prompt values can change meaning under older compatibility modes

Affects noxSource GCVE Database

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Authoritative record:CVE-2026-113723· High 7.1

Not known to be exploited · CVSS 7.1 High : upgrade to 2026.10.20 or 2022.8.7_1 soon.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 4.0 base score

7.1High

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 4.0	7.1

EPSS: 0.2% chance of exploitation in 30 days – higher than 15% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2026.10.20, 2022.8.7_1

CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Attack Vector: Local
Attack Complexity: High
Attack Requirements: Present
Privileges Required: None
User Interaction: Active
Vulnerable system confidentiality: High
Vulnerable system integrity: High
Vulnerable system availability: High
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity: High: The successful attack depends on the evasion or circumvention of security-enhancing techniques in place that would otherwise hinder the attack. These include: Evasion of exploit mitigation techniques, for example, circumvention of address space randomization (ASLR) or data execution prevention (DEP) must be performed for the attack to be successful; Obtaining target-specific secrets. The attacker must gather some target-specific secret before the attack can be successful. A secret is any piece of information that cannot be obtained through any amount of reconnaissance. To obtain the secret the attacker must perform additional attacks or break otherwise secure measures (e.g. knowledge of a secret key may be needed to break a crypto channel). This operation must be performed for each attacked target.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Active: Successful exploitation of this vulnerability requires a targeted user to perform specific, conscious interactions with the vulnerable system and the attacker’s payload, or the user’s interactions would actively subvert protection mechanisms which would lead to exploitation of the vulnerability.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 20 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade nox to 2026.10.20 or 2022.8.7_1.

Affected software

Product	Affected	Fixed in
Homebrewnox`pkg:brew/nox`Other threats	Affected >=2020.12.31 <2022.8.7_1 >=2023.4.22_1 <2026.10.20	Fixed in 2022.8.7_1 2026.10.20

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

## Summary Caller-supplied prompt text can become executable syntax in the bash activation prompt. An attacker must influence the value passed to virtualenv, and a user must subsequently activate the environment and draw the prompt. ## Affected area Bash runs with compatibility level 4.2 and draws the environment prompt. Its replacement-string behavior differs from newer compatibility modes, leaving prompt text subject to a second interpretation. The report concerns POSIX activation. It does not establish exposure through unrelated activators. ## Attacker-controlled input The attacker controls prompt or destination data passed as a virtualenv argument. The user later sources the generated activation script. ## Affected code The relevant 21.14.8 source is in [bash prompt assembly](https://github.com/pypa/virtualenv/blob/a795ab116356afde11039cf2763d77e8a06da738/src/virtualenv/activation/bash/activate.sh). ## Mechanism `bin/activate` copies the prompt into `PS1`. A shell expands `PS1` again when it draws a prompt, so the value must survive both the assignment and that later expansion. The bash and zsh branches escape for their usual prompt rules. Three other paths still interpret prompt data as commands: dash sourcing `activate` directly, a child dash inheriting an exported `PS1` from bash, and bash running at compatibility level 4.2 or lower. A value such as `x$(touch MARKER)y` then runs `touch` on prompt display. Creating the environment does not run the payload. ## Reproduction and evidence The scanner's child-shell reproducer creates an environment with `--prompt 'x$(touch MARKER)y'`, sources `bin/activate` in interactive bash, and starts interactive `sh` (dash). Its control leaves `PS1` unexported: neither shell creates `MARKER`. With `PS1` exported, bash displays the prompt without executing the value, but the child dash creates `MARKER`; the reproducer ends in `BUG`. The report gives separate console reproductions for direct dash activation and bash compatibility level 4.2. The child-shell path can arise after another environment's activation has exported `PS1`. The scanner linked this finding to [#3326](https://github.com/pypa/virtualenv/pull/3326) and its follow-up #3390. Those changes cover the usual bash path but leave the three paths above. The proposed change in [#3418](https://github.com/pypa/virtualenv/pull/3418) keeps a variable reference in `PS1`, so prompt text is expanded as data when drawn. The private report's reproducer was run by the scanner; the later command-execution result was supplied by the maintainer review. This advisory does not claim that every POSIX shell or every bash mode is affected. ## Introduced The report traces direct dash sourcing to the first 20.x activator (20.0.0b1), and inherited `PS1` to #3390 (first released in 21.14.7). It demonstrates the compatibility-level case on bash 5.2. Those historical boundaries come from the report; the release confirmed by the maintainer is 21.14.8. ## Attack sequence ```mermaid sequenceDiagram participant A as Prompt supplier participant V as virtualenv participant B as Interactive bash participant D as Child dash A->>V: --prompt x$(touch MARKER)y V->>B: generated bin/activate B->>B: assign escaped prompt to PS1 alt PS1 is not exported B->>D: start sh with its own PS1 D-->>B: marker absent else PS1 is exported B->>D: start sh with inherited PS1 D->>D: expand $(touch MARKER) on prompt draw D-->>B: marker created end ``` ## Reproducer files The following files are from the scanner report for `ANT-2026-1MOI2X3T`. They were tested against commit `a857a7823c73` in the scanner image. The `repro` entrypoint expects companion files under `/tmp/repro.d`; cases that change user IDs need a disposable root-capable container. The last output line is `BUG` when the reported behavior occurs. These files are included as evidence and were not rerun for this advisory update. **`repro`** ```text #!/usr/bin/env python3 import shutil import subprocess from pathlib import Path work = Path("/tmp/repro-inherited-ps1") shutil.rmtree(work, ignore_errors=True) work.mkdir() marker = work / "MARKER" print("sh is", Path("/bin/sh").resolve()) # attacker: only the text a tool such as tox or hatch relays as --prompt hostile_prompt = f"x$(touch {marker})y" # set up: the environment, made with the virtualenv command subprocess.run( ["virtualenv", "--no-periodic-update", "--without-pip", "--activators", "bash", "--prompt", hostile_prompt, str(work / "env")], check=True, stdout=subprocess.DEVNULL, ) assert not marker.exists(), "creating the environment must not run the prompt" # user: in an interactive bash, source bin/activate, then start sh. # -i makes both shells draw their prompt although stdin is not a terminal; sh draws one, reads EOF and returns session = Path("/tmp/repro.d/user_session.sh").read_text() interactive_bash = ["bash", "--norc", "--nopr

References

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