# CVE-2026-83557: jackson-databind omits java.lang.Comparable from DefaultBaseTypeLimitingValidator's unsafe base types > Attackers can instantiate arbitrary Comparable classes via polymorphic deserialization, potentially enabling path traversal or data access in applications using default validators. - **Severity:** Medium 5.6 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 1 Sep 2026 - **Updated:** 1 Sep 2026 - **Also known as:** CLEANSTART-2026-BM20814, CLEANSTART-2026-CI22056, CLEANSTART-2026-DP01123, CLEANSTART-2026-HB03857, CLEANSTART-2026-HR33397, CLEANSTART-2026-HZ51336, CLEANSTART-2026-JJ71926, CLEANSTART-2026-LT75275, CLEANSTART-2026-PV37288, CLEANSTART-2026-SN44747, CLEANSTART-2026-SY78666, CLEANSTART-2026-UI48167, CLEANSTART-2026-UZ99308, CLEANSTART-2026-XY46108, DEBIAN-CVE-2026-83557, ECHO-a123-f4fc-2053, GHSA-gx83-3vf8-gh7j, MINI-262r-mgqx-cfx4, MINI-27r8-353v-mpcf, MINI-29x6-6wcp-x376, MINI-2jmx-pmp7-hgxh, MINI-2q66-v8mw-26px, MINI-2vmq-xgx5-hw27, MINI-367x-f94c-34p3, MINI-3958-3594-phvc, MINI-3gcp-jvhc-5xm6, MINI-3vc2-552p-q8p8, MINI-3vp6-prvj-385q, MINI-3w5g-w8fm-xg5c, MINI-3w7x-3gmj-gpg6, MINI-42vh-4jff-qj7h, MINI-432v-28p4-6vf6, MINI-43mc-v49p-p7w5, MINI-47mc-q6pm-8gv8, MINI-4cpp-2qf2-9q2h, MINI-4f48-rm35-8g9j, MINI-4h6w-ww9w-752h, MINI-4hwm-65g7-jvrm, MINI-4jjr-mv7v-vf3x, MINI-4jx4-2r64-5q6p, MINI-4qmc-h3x7-xjx9, MINI-4r2h-jhq9-gj53, MINI-57jr-6h25-vvcc, MINI-5cp6-q3qm-5m74, MINI-5p5c-6mcg-vvrm, MINI-5rqh-3m2h-f85m, MINI-5vc5-3mm8-5qf7, MINI-63hp-jj7v-fmjc, MINI-679c-6ch9-2x7p, MINI-6g36-g3cp-7frp, MINI-6rff-crv2-38c8, MINI-6x48-2m5p-w364, MINI-749m-82wq-h9mr, MINI-777f-rcm4-m6j7, MINI-78vg-rxrj-hwpr, MINI-7fqg-wc4r-x7q3, MINI-7j55-pvvr-hx79, MINI-7vcg-gx5q-942m, MINI-85ww-5rww-hx3f, MINI-86hr-cxc8-rhg4, MINI-87m3-r32j-x2px, MINI-8hxv-46mq-hjq3, MINI-8q59-pg4p-c74p, MINI-8qvj-563r-6vmc, MINI-8wpj-4qhx-9mvg, MINI-92qx-x5h6-3h33, MINI-959q-qfh2-vm97, MINI-95f8-2jpw-4xcr, MINI-9hj9-qh68-29wx, MINI-9qp6-jj97-7q94, MINI-9r8x-3jw5-5crh, MINI-c2mg-3w67-75jv, MINI-c73w-959g-5c36, MINI-c75g-fc9r-j93p, MINI-cg69-4cgx-fvhq, MINI-cp7m-gpwh-xvh4, MINI-cvr6-cv5g-2m6v, MINI-cwcg-29rq-xvqc, MINI-cwg8-8jpx-wxjp, MINI-cxvg-m3h3-x5xq, MINI-f274-7q5c-qpcx, MINI-f7ph-rqjh-3f2h, MINI-f92w-q992-v5j6, MINI-fjwg-xq56-47cj, MINI-frmp-jf56-42vq, MINI-fwj2-7hh8-w8q7, MINI-fxhq-98g8-r63p, MINI-g2hp-f2jc-v9w3, MINI-g77v-74hv-9mwm, MINI-gc6x-wrhm-83q3, MINI-ghr2-xp32-h5q6, MINI-gvm5-m563-pmrr, MINI-h976-5v9p-hxmw, MINI-j29r-p496-684w, MINI-j32g-4xm9-c9ph, MINI-j7w9-xq79-mh3h, MINI-jfvf-wwp6-6j6m, MINI-jh7h-q424-m57r, MINI-jhqq-9q63-f7pj, MINI-jm9f-4gqm-x7j9, MINI-jpwc-8rf2-h9p5, MINI-jq8w-3fgr-m5q5, MINI-jvvw-v538-m5j4, MINI-jw67-76rf-pmvh, MINI-p3vr-qv6q-87fp, MINI-p7hx-rjwj-jvjw, MINI-pcp5-244j-hgrj, MINI-q7mm-99x6-gww7, MINI-qxw5-f455-34xp, MINI-r2w5-97wv-5cjj, MINI-r4xc-q4xv-cxg2, MINI-r636-f234-4m76, MINI-r7j2-r52h-m225, MINI-r84m-5gvc-qcm3, MINI-rg56-7rv2-ppgw, MINI-rwj4-9fc9-mmhj, MINI-vmcj-hfwm-8x5f, MINI-vqjh-4mwv-7852, MINI-vrm7-79wf-8gqc, MINI-w376-qwmh-9jm6, MINI-w492-8v8v-mh3w, MINI-w63v-6j4q-6hp7, MINI-w8mj-vgw8-3w85, MINI-whrq-7g57-pmp2, MINI-wmpq-cc7r-mpjq, MINI-wwr7-88gr-4535, MINI-x4jv-rrmp-39j9, MINI-xc29-m3hf-r96w, MINI-xhcx-p4p6-f9qh, ROOT-APP-MAVEN-CVE-2026-83557, UBUNTU-CVE-2026-83557 ## What is CVE-2026-83557? CVE-2026-83557 is a medium-severity unsafe deserialization vulnerability in FasterXML jackson-databind, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description DefaultBaseTypeLimitingValidator is the PolymorphicTypeValidator applied automatically whenever @JsonTypeInfo is used without an explicitly configured custom validator. It denies polymorphic resolution only for a fixed set of "unsafe base types", and its isSafeSubType method returns true unconditionally for every base type outside that set. java.lang.Comparable was absent from the list despite being implemented by a very large fraction of JDK and application classes, comparable in breadth to java.io.Serializable, which is on the list for that reason. An application declaring an @JsonTypeInfo-annotated property or class with Comparable as its base type, and no custom PolymorphicTypeValidator, will accept a type identifier for essentially any class implementing Comparable. This yields an attacker-controlled object instantiation primitive; a demonstrated case constructs a java.io.File for an arbitrary attacker-chosen path, which becomes path-traversal-adjacent if the application subsequently calls path-sensitive methods on the value. No class implementing Comparable has been identified that yields code execution through deserialization alone. Global Default Typing via activateDefaultTyping is not affected, because that method structurally requires an explicit PolymorphicTypeValidator argument. This affects com.fasterxml.jackson.core:jackson-databind from 2.11.0 before 2.18.10, from 2.19.0 before 2.21.6, and from 2.22.0 before 2.22.2, and tools.jackson.core:jackson-databind from 3.0.0 before 3.1.6 and from 3.2.0 before 3.2.2. Users should upgrade to 2.18.10, 2.21.6, 2.22.2, 3.1.6, or 3.2.2. Weakness: CWE-915 (Improperly Controlled Modification of Dynamically-Determined Object Attributes), CWE-502 (Deserialization of Untrusted Data) ## Which versions are affected by CVE-2026-83557? 10 open source packages ship an affected version, including com.fasterxml.jackson.core:jackson-databind and tools.jackson.core:jackson-databind. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.11.0 | 2.18.10 | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.11.0 | 2.18.10 | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.19.0 | 2.21.6 | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.19.0 | 2.21.6 | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.22.0 | 2.22.2 | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.22.0 | 2.22.2 | | `tools.jackson.core:jackson-databind` | Maven | From 3.0.0 | 3.1.6 | | `tools.jackson.core:jackson-databind` | Maven | From 3.0.0 | 3.1.6 | | `tools.jackson.core:jackson-databind` | Maven | From 3.2.0 | 3.2.2 | | `tools.jackson.core:jackson-databind` | Maven | From 3.2.0 | 3.2.2 | ## How do I fix CVE-2026-83557? Upgrade com.fasterxml.jackson.core:jackson-databind to a fixed version for your release line: 2.18.10, 2.21.6 or 2.22.2. ## Is CVE-2026-83557 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-83557 exists. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-83557 and fix it if it is affected. What it is: CVE-2026-83557 is a medium-severity unsafe deserialization vulnerability in FasterXML jackson-databind, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-83557 exists. Affected packages and fixed versions: - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.11.0; fixed in 2.18.10 - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.11.0; fixed in 2.18.10 - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.19.0; fixed in 2.21.6 - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.19.0; fixed in 2.21.6 - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.22.0; fixed in 2.22.2 - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.22.0; fixed in 2.22.2 - tools.jackson.core:jackson-databind (Maven): affected from 3.0.0; fixed in 3.1.6 - tools.jackson.core:jackson-databind (Maven): affected from 3.0.0; fixed in 3.1.6 - tools.jackson.core:jackson-databind (Maven): affected from 3.2.0; fixed in 3.2.2 - tools.jackson.core:jackson-databind (Maven): affected from 3.2.0; fixed in 3.2.2 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-83557/ (Markdown: https://insights.sbomify.com/CVE-2026-83557/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-83557 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-83557 - OSV: https://osv.dev/vulnerability/CVE-2026-83557 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-83557/ Summaries are generated and may contain mistakes; the official description above is the record.