VulnerabilityPublished 14 Oct 2026Updated 29 Oct 2026

CVE-2026-106439: Hydra · Mutable instantiate policy sets allow target blocklist bypass

Affects dvcSource GCVE Database

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Authoritative record:CVE-2026-106439· High 8.5

Not known to be exploited · CVSS 8.5 High : upgrade to 3.67.1_16 soon.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 4.0 base score

8.5High

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 39% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.67.1_16

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

Attack Vector: Local
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: Passive
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: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
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: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
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 6 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 dvc to 3.67.1_16.

Affected software

Product	Affected	Fixed in
Homebrewdvc`pkg:brew/dvc`Other threats	Affected >=3.67.1_10 <3.67.1_16	Fixed in 3.67.1_16

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

Description

## Summary Hydra's legacy `instantiate()` target blocklists and related execution-policy collections are stored in mutable module-level state. Because `_locate()` can resolve attributes on imported objects, a configuration can resolve a mutation method such as `.discard()`, modify the active policy, and then instantiate a target that would otherwise be blocked. ## Impact A configuration controlling multiple sibling `_target_` entries can first remove an entry from a target blocklist and then invoke the removed target. Sibling nodes are processed in insertion order and consult the same mutable module-level policy. This affects the legacy/default path without an execution whitelist. The 1.3 blocklist is a defense-in-depth measure rather than a complete security boundary, and applications must not treat arbitrary untrusted configuration as safe to instantiate or use for Python logging configuration. Released `hydra-core` versions 1.3.4 through 1.3.6 and 1.4.0.dev4 through 1.4.0.dev9 are affected. Fixed releases are 1.3.7 and 1.4.0.dev10. The reported direct mutation path does not bypass an execution whitelist restricted to intended application targets and supplied by trusted Python code. During remediation, Hydra additionally hardened generic discovery, dispatch, introspection, alias, callable-result, and deferred-callable paths that could otherwise undermine name-only authorization. ## Technical details In `hydra-core` 1.3.4 and 1.3.5, the mutable blocklist is reachable as: `hydra._internal.instantiate._instantiate2.DEFAULT_BLOCKLISTED_MODULES` In `hydra-core` 1.3.6, the expanded policy includes mutable collections in: `hydra._internal.target_policy` For example: `hydra._internal.target_policy.UNCONTROLLED_EXECUTION_TARGETS.discard` resolves to the bound `set.discard` method. The mutation target itself is not blocked on the legacy path. Once an entry is removed, subsequent authorization checks observe the modified set. Other runtime policy collections can be attacked similarly by removing denied entries or adding entries to exception sets. Because the collections are module-level state, a successful mutation persists for the lifetime of the Python process unless explicitly reversed. ## Safe reproduction The behavior in `hydra-core` 1.3.6 can be demonstrated without invoking a shell command. The `finally` block restores the modified process-global state: ```python from omegaconf import OmegaConf from hydra._internal.target_policy import UNCONTROLLED_EXECUTION_TARGETS from hydra.utils import instantiate target = "builtins.eval" assert target in UNCONTROLLED_EXECUTION_TARGETS try: result = instantiate( OmegaConf.create( { "disarm": { "_target_": ( "hydra._internal.target_policy." "UNCONTROLLED_EXECUTION_TARGETS.discard" ), "_args_": [target], }, "proof": { "_target_": target, "_args_": ["40 + 2"], }, } ) ) assert result["proof"] == 42 assert target not in UNCONTROLLED_EXECUTION_TARGETS finally: UNCONTROLLED_EXECUTION_TARGETS.add(target) ``` ## Remediation The fix makes runtime policy state immutable and integrity checked, and prevents declarative configuration from accessing or mutating Hydra internals and protected Python implementation state. Target authorization now covers canonical resolved identities, aliases, discovery results, callable results, deferred callables, and runtime arguments. The patch also rejects configuration-driven code, policy, and process- environment mutation, along with unsafe introspection and formatting traversal that can expose protected runtime capabilities. Hydra 1.3.7 receives these protections as defense in depth; it does not make untrusted configuration sandboxed. Hydra 1.4 additionally uses a trusted, narrowly scoped execution whitelist as the supported security boundary for declarative instantiation and Hydra-controlled Python logging configuration. Users should upgrade to `hydra-core` 1.3.7 on the stable line or 1.4.0.dev10 on the development line. ## Workarounds Do not pass configuration from untrusted sources to `instantiate()` or to Hydra-controlled Python logging configuration. The 1.3 release line has no execution-whitelist facility, so users who cannot upgrade immediately must restrict configuration input to trusted sources. On affected 1.4 development releases, applications can also supply a trusted, narrowly scoped execution whitelist from Python code. The whitelist itself must not be derived from untrusted configuration. Restart any long-running process that may already have instantiated untrusted configuration, because a policy mutation persists in process-global state.

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